Iron is an essential element for bacterial growth. An excess of iron can enhance bacterial virulence and compromise many host defense mechanisms. Iron in the human body is bound to proteins and not easily available to bacteria. Bacteria, however, can grow readily in saliva in vitro and in the oral cavity. We hypothesize the growth occurs because, unlike other body fluids, iron is readily available to bacteria in saliva. Surprisingly little is known about the availability of iron in saliva. This small grant proposal is to explore the validity of our hypothesis. The specific aims of this study are: (1) To investigate the availability of iron in parotid saliva by determining the Unsaturated Iron Binding Capacity (UIBC) and the concentration of Lactoferrin (LF) in saliva. (2) To investigate the role of iron in the ability of oral bacteria to grow in parotid saliva. The UIBC of parotid saliva will be determined by subtracting total iron (TI) from total Iron Binding Capacity (TIBC). The TI and TIBC will be determined by flameless atomic absorption spectroscopy and the LF will be determined by and ELISA method. The role of iron in the bacterial growth in saliva will be determined by comparing the growth of S. Sanguis in parotid saliva in presence or absence of the iron- chelating protein apotransferrin. Our hypothesis will be supported if these studies demonstrate that parotid saliva has little or no UIBC and that the growth of S. Sanguis is inhibited by apotransferrin. These studies may also indicate that LF is not the major iron binding protein in saliva. The directions for further study include examining the role of salivary and gingival crevicular fluid iron in dental diseases and investigating the mechanism of iron uptake by periodontopathic bacteria. Such studies may eventually lead us to develop diagnostic and therapeutic measures based upon the iron uptake of the pathogens of the dental plaque.